Random Fedora 28 freeze, no keyboard input

I have near-new Fedora 28 installation that randomly locks up but the keyboard can't be used. The mouse pointer moves around tge screen, but if I try to hit the "power" icon using the mouse - nothing because everything is frozen.
It doesn't matter if I use gnome or gnome-classic.
The only solution is to hold down the power button.
- this can't be good for the mechanical HDD
Has anybody any tips ?